A demand for higher positional accuracy in placing electronic components onto boards is increasing, and in response, methods are commonly adopted that use image recognition for correcting a positional deviation of an electronic component and board when placing the electronic component onto the board. Examples of this type of electronic component placement machine are disclosed in Japanese Laid-open Applications Nos. H2-56945 and H2-56944.
The machine disclosed in No. H2-56945 is equipped with a flipping device for removing an electronic component from a feeder, and flipping and transferring the electronic component to a predetermined transfer position; and a placement head for receiving and holding this flipped electronic component and then transferring and placing it onto a board.
The electronic component held by the placement head is recognized by a camera to position the component for placement. This technology enables high-speed placement of electronic components with bumps. Operability and positional accuracy are also high.
However, further improvements in productivity are needed as production technology advances rapidly in the electronic component industry.
In the prior art, a placement head needs to stop briefly after receiving an electronic component to allow a camera to recognize the component.
As a result, loss of time often occurs due to reduction of speed of the placement head, on the way to a board, for stopping. This results in a barrier to further reduction of cycle time.
The machine disclosed in No. H2-56944 is equipped with a flipping device for removing an electronic component from a feeder, and flipping and transferring the electronic component to a predetermined transfer position; and a placement head for receiving and holding this flipped electronic component and placing it onto a board. This machine has a pre-centering recognition function to allow the placement head to receive the electronic component after recognizing the flipped electronic component via a camera. This technology. enables placement of an electronic component, with bumps, onto a board with high positional accuracy, after flipping the electronic component.
However, in the above prior art, the placement head needs to retract from a transfer position for standby because pre-centering recognition is executed at the transfer position. A time loss occurs in some cases due to reduction of speed for reducing or stopping movement of the placement head on the way to the transfer position. This provides a limit to reducing cycle time, creating a need for an electronic component placement machine with higher performance.
Moreover, conventional electronic component placement machines for flip chips (hereinafter referred to as “chips”) need to provide a component placement level for a board that is significantly higher than a component transfer level for transporting an electronic component, removed from a feeder, to a placement head due to various limitations in machine design. If a difference between these levels is entirely accounted for by vertical movement of the placement head, a lengthened stroke of a z-axis driving mechanism for elevating the placement head typically causes deflection of a shaft, resulting in lower mounting accuracy. If rigidity of the z-axis driving mechanism is improved so as to prevent this type of failure, problems emerge with high-speed operation and brief stoppage due to increased mass of the placement head. This may also result in a longer cycle time.
The present invention aims to offer an electronic component placement machine and electronic component placement method for improving productivity by reducing cycle time while securing mounting accuracy.